The shrinking dimensions of active devices on silicon chips are approaching its limit due to restrictions set by photolithographic techniques. For example, wave properties of radiation, such as interference and diffraction, can limit device size and density. Considerable research has taken place to overcome the limitations of photolithographic techniques.
Carbon-based nano-materials are considered one type of alternative materials for manufacturing active devices. One example of a nano-material is carbon nanotubes, which are tubular carbon molecules with properties that make them potentially useful in extremely small scale electronic and mechanical applications. They exhibit high strength and advantageous electrical properties, and are extremely efficient conductors of heat. Also, because of their unique dimensions and unusual current conduction mechanism, carbon nanotubes may be ideal components of electrical circuits, transistors, MEMS devices, interconnects, and other circuit elements. FIG. 1 illustrates a carbon nanotube 100 having carbon atoms along the surface of the cylindrical shape and a hemispherical shape in its end portions. The carbon nanotube 100 has a metallic or semiconductor property depending on the number of carbon atoms constituting the cylindrical shape and the coupling direction of them.
One problem with using nano-materials such as carbon nanotubes in circuits relates to fabrication difficulties. The carbon nanotube production processes are very different from the traditional integrated circuit (IC) fabrication process in that a conventional top-to-bottom approach is not used (e.g., films are deposited onto a wafer and pattern-etched away). Today, there is no reliable way to arrange carbon nanotubes into a circuit. In one currect fabrication method, carbon nanotubes are manipulated one-by-one with the tip of an atomic force microscope in a painstaking, time-consuming process.